Why wasn‘t the 3950X a valid choice? It is to work well with Linux but Intel is better for the job with its 14 cores?
Also, can recommend the ASUS Pro WS X570-Ace for the use with many PCIe devices even though it‘s only AM4. When using PCIe 3.0 you can use 34 lanes for AICs with risers/M.2/U.2 adapters with a low probability of hitting a PCIe lane bottleneck, pretty neat (x4/x4/x4/x4/x4/x4/x8/x2).